The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Mounjaro And Sulfur Burps — What You Need To Know
Sulfur burps (also called "rotten egg" belching) are a reported side effect some people experience when taking Mounjaro (tirzepatide), particularly in the early weeks of treatment. These occur because the medication slows gastric emptying, allowing food to ferment longer in the stomach. While unpleasant, they typically improve as your body adjusts to the dose. This guide explains what causes them, how long they last, and what your options are for accessing Mounjaro in the UK — both through NHS specialist services and private prescription routes.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Understanding Mounjaro Sulfur Burps And Side Effects
Sulfur burps happen because Mounjaro slows how quickly food moves through your stomach, which is part of how the medication works to help regulate appetite. When food sits in the stomach longer, natural bacteria break it down, producing gases that smell like sulphur or rotten eggs. This is most common in the first 4–8 weeks of treatment or when doses are increased.
- Usually mild and improve within 2–4 weeks as your body adjusts
- More likely if you eat fatty, high-protein, or difficult-to-digest foods
- Can be reduced by eating smaller, more frequent meals
- Drinking plenty of water and avoiding carbonated drinks may help
- Taking simethicone (an over-the-counter remedy) may provide relief
Other common Mounjaro side effects include nausea, diarrhoea, constipation, and indigestion. Most are temporary and improve as your body adjusts. If sulfur burps persist beyond 8 weeks or are severely distressing, contact your prescriber — they may suggest dose adjustments or additional support.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Accessing Mounjaro In The UK — Cost And Options
NHS route: Mounjaro is available through specialist tier 3 weight management services following NICE approval. You'll need a referral from your GP and assessment by the specialist service. Availability and waiting times vary significantly by region. Some areas have waiting lists of several months.
Private route: You can access Mounjaro through UK-licensed online prescribers without NHS referral. After an online clinical assessment, a prescription is issued and dispensed by a GPhC-registered pharmacy. Costs range from approximately £129–£320 per month depending on dose. The lowest doses (2.5–5mg) are typically cheapest; higher doses (10–15mg) cost more. Payment is usually per injection or per 4-week supply (one KwikPen).
Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses before starting treatment.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How long do Mounjaro sulfur burps last?
Most people find sulfur burps improve within 2–4 weeks as their body adjusts to the medication. They're most noticeable in weeks 1–4 and often after dose increases. If they persist beyond 8 weeks, mention this to your prescriber — dietary adjustments or dose timing changes may help.
What's the difference between Mounjaro and Wegovy for cost in the UK?
Both are prescription-only and available privately in the UK. Mounjaro (tirzepatide) and Wegovy (semaglutide) have similar private cost ranges (£129–£320/month depending on dose). Individual prescriber costs vary. NHS availability also varies by region, though both are now NICE-approved for specialist services.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is now approved by NICE for use within NHS specialist tier 3 weight management services. You'll need a GP referral and assessment. Availability and waiting times depend on your region and local ICB (integrated care board). Some areas have lengthy waiting lists; others may have shorter access times.
How much does a Mounjaro KwikPen cost privately in the UK?
Private costs range from approximately £129–£320 per month depending on the dose and prescriber. Each KwikPen contains 4 weekly doses. Starting doses (2.5–5mg) are usually cheaper; maintenance doses (10–15mg) cost more. Costs may vary between different online prescribing services, so it's worth comparing.
What should I eat to reduce sulfur burps on Mounjaro?
Eat smaller, more frequent meals rather than large portions. Choose easily digestible foods like white rice, chicken, pasta, and vegetables. Avoid fatty, greasy, fried, and high-protein meals initially, as these ferment longer in the stomach. Drink plenty of water and avoid fizzy drinks, which can worsen burping.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.